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I want to set OpacityMask to a control, but I need to build that mask dynamically. Here is how it should look:


The width and height of the whole (red) rectangle is dynamic, based on width and height of parent control. But I need to place two small rectangles (static width and height) in top left and top right corner, as shown on image. So how can I make this happen?

I tried this code, but it doesn't work: (nothing is displayed at all)

<Border BorderBrush="#80FFFFFF" BorderThickness="1" CornerRadius="5">
    <Border.OpacityMask>
        <VisualBrush>
            <VisualBrush.Visual>
                <DockPanel>
                    <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Height="2">
                        <Border Background="Transparent" Width="12" VerticalAlignment="Stretch" HorizontalAlignment="Left" />
                        <Border Background="Black" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" />
                        <Border Background="Transparent" Width="12" VerticalAlignment="Stretch" HorizontalAlignment="Right" />
                    </StackPanel>

                    <Border Background="Black" />
                </DockPanel>
            </VisualBrush.Visual>
        </VisualBrush>
    </Border.OpacityMask>
</Border>

Is it even valid to use VisualBrush this way (as a OpacityMask)?

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1 回答 1

3

如果我正确理解您的问题，您是否希望图像中的那些黑色方块是透明的？

更新：在此处上传示例项目：http ://www.mediafire.com/?5tfkd1cxwfq0rct

我认为问题在于Panel内部VisualBrush不会伸展。Panel您可以通过将您使用的任何内容的宽度和高度绑定到实际宽度和实际高度来获得所需的效果Border

<Border Name="border" BorderBrush="Red" BorderThickness="1" CornerRadius="5">
    <Border.OpacityMask>
        <VisualBrush>
            <VisualBrush.Visual>
                <Grid Width="{Binding ElementName=border, Path=ActualWidth}"
                      Height="{Binding ElementName=border, Path=ActualHeight}">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="20"/>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="20"/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="20"/>
                        <RowDefinition Height="*"/>
                    </Grid.RowDefinitions>
                    <Rectangle Fill="Transparent" Grid.Column="0"/>
                    <Rectangle Fill="Black" Grid.Column="1"/>
                    <Rectangle Fill="Transparent" Grid.Column="2"/>
                    <Rectangle Fill="Black" Grid.Row="1" Grid.ColumnSpan="3"/>
                </Grid>
            </VisualBrush.Visual>
        </VisualBrush>
    </Border.OpacityMask>
    <Grid>
        <TextBlock Text="Testing OpacityMask with a rather long string................." Grid.ZIndex="3"/>
        <Rectangle Fill="Green"/>
    </Grid>
</Border>

再次更新
Decorator Child 的 DropShadowEffectBorder似乎推动了BorderVerticaly 和 Horizo​​ntaly 的 OpacityMask。更糟糕的是它似乎是堆叠的，所以在你的例子中，当你有三个嵌套的 DropShadowEffects 时Decorators， BlurRadius 的总和是 45 (20+15+10) 所以 OpacityMask 被推入 45 的值（在至少看起来这是怎么回事，但有点难以分辨..）。您可以尝试通过增加 ColumnDefinition Widths 和 RowDefinition Heights 来弥补这一点，但我认为很难找到动态解决方案。

解决问题的更好方法可能是使用Border.Clip，但这也不容易。

Point1:  0, 2
Point2: 12, 2
Point3: 12, 0
Point4: Width of Border - 12, 0
Point5: Width of Border - 12, 2
Point5: Width of Border, 2
Point6: Width of Border, Height of Border
Point7: 0, Height of Border

更新 3
提出了一个不需要这么多绑定的更好解决方案。创建一个派生自Border并覆盖 GetLayoutClip 的自定义类。这适用于 Designer 和 Runtime。为了增加灵活性，ClippedBorder您可以引入一些依赖属性来代替硬编码的 2 和 12。这里的新示例应用程序：http ://www.mediafire.com/?9i13rrqpbmzdbvs

public class ClippedBorder : Border
{
    protected override Geometry GetLayoutClip(Size layoutSlotSize)
    {
        PathGeometry pathGeometry = new PathGeometry();
        pathGeometry.Figures = new PathFigureCollection();

        //Point1:  0, 2
        PathFigure pathFigure = new PathFigure();
        pathFigure.StartPoint = new Point(0, 2);

        //Point2: 12, 2
        LineSegment lineSegment1 = new LineSegment();
        lineSegment1.Point = new Point(12, 2);

        //Point3: 12, 0
        LineSegment lineSegment2 = new LineSegment();
        lineSegment2.Point = new Point(12, 0);

        //Point4: Width of Border - 12, 0
        LineSegment lineSegment3 = new LineSegment();
        lineSegment3.Point = new Point(this.ActualWidth-12, 0);

        //Point5: Width of Border - 12, 2
        LineSegment lineSegment4 = new LineSegment();
        lineSegment4.Point = new Point(this.ActualWidth-12, 2);

        //Point5: Width of Border, 2
        LineSegment lineSegment5 = new LineSegment();
        lineSegment5.Point = new Point(this.ActualWidth, 2);

        //Point6: Width of Border, Height of Border
        LineSegment lineSegment6 = new LineSegment();
        lineSegment6.Point = new Point(this.ActualWidth, this.ActualHeight);

        //Point7: 0, Height of Border 
        LineSegment lineSegment7 = new LineSegment();
        lineSegment7.Point = new Point(0, this.ActualHeight);

        pathFigure.Segments.Add(lineSegment1);
        pathFigure.Segments.Add(lineSegment2);
        pathFigure.Segments.Add(lineSegment3);
        pathFigure.Segments.Add(lineSegment4);
        pathFigure.Segments.Add(lineSegment5);
        pathFigure.Segments.Add(lineSegment6);
        pathFigure.Segments.Add(lineSegment7);

        pathGeometry.Figures.Add(pathFigure);

        return pathGeometry;
    }
}
于 2011-02-13T02:10:52.797 回答